Diagnosis of night blindness through standardized interview and electroretinography

Introduction: vitamin A deficiency (VAD) is one of the biggest problems in public health worldwide, and night blindness (NB) is the first functional change caused by deficiency of this vitamin. In this context, electroretinography stands out as the gold-standard diagnostic method; however, it is a high-cost method and its applicability in clinical practice presents some difficulties. Objective: to compare NB diagnosis through the use of the standardized interview issued by the World Health Organization/Pan American Health Organization (WHO/PAHO) and with electroretinography, and to evaluate the association of these diagnoses with serum concentrations of retinol in individuals with class III obesity. Methods: adult patients of both genders, in the 20-60 years age group, with BMI >= 40 kg/m(2), were studied. NB was diagnosed through electroretinography and the standardized interview validated by the WHO/PAHO. Serum retinol was quantified by the HPLC-UV method, and VAD was diagnosed when levels were < 1.05 mu mol/L; severity was also evaluated. The statistical analysis was carried out using the Statistical Package for the Social Sciences, version 21.0 (p < 0.05). Results: mean BMI was 44.9 +/- 11.8 kg/m(2), and a negative correlation was found for serum levels of retinol (p = 0.01). The prevalence of VAD, according to the serum concentration of retinol, was 14 %; of this percentage 23.3 % had NB according to the standardized interview, and 22.0 % according to electroretinography. NB as diagnosed by both methods showed an association with VAD according to serum concentrations of retinol. Of these individuals with NB, according to the standardized interview, 6.9 % had severe VAD, 10.3 % moderate VAD, and 82.8 % marginal VAD. Conclusion: the standardized interview for the diagnosis of NB can be a good strategy to evaluate the nutritional status of vitamin A, and it is a simple, non-invasive, low-cost method.